CAD interoperability around the JT neutral format

JT (Jupiter Tessellation) is an ISO standardized, open 3D CAD data exchange format used for product visualization, collaboration, digital mockups, and other purposes. Developed by Siemens, the JT format can contain any combination of meshed (faceted) data, surfaces (NURBS), product manufacturing information (PMI), and metadata (textual attributes) either exported from the native CAD system or inserted by a product data management (PDM) system. The JT format contains an assembly tree representation of nested sub-assemblies of parts with specific CAD attributes. Facet (triangle) information is stored using geometric compression techniques. Visual scene and 3D model attributes such as lights, textures, and/or materials are supported.

JT was designed to enable interactive display of very large assemblies (i.e., containing tens of thousands of components). The JT file format is capable of storing a very large number of faceted representations with varying levels of detail (LODs). When the entire product is displayed, the application shows only a simple and coarse model. However, as the user zooms in on an area, progressively finer representations are loaded and displayed, and non-visible representations are unloaded to conserve memory.

The JT format supports a wide range of engineering data. This data can be very light, containing little more than facet data, or it can be quite rich, containing complete NURBS geometric representations, as well as product structures, attributes, metadata, and manufacturing information (PMI).

  • Product structure - assembly, part, instance
  • Facet - polygon, set of polygons
  • Lighting - set of lights, point light, infinite light
  • Geometry and precise topology - point, curve, surface, face, loop, edge, vertex
  • B-rep representation - JT B-rep and XT B-rep (Parasolid), and STEP B-rep will be supported by ISO JT V2
  • Geometry primitive - box, cylinder, pyramid, sphere
  • Product and manufacturing information (PMI) - GD&T, 3D annotations
  • Attributes/properties - text, integer, float, date, layers

The product structure can be represented in a variety of JT file configurations. JT supports the following file structures:

  • By Part - All assembly nodes in a product structure hierarchy are stored in a single JT file, and each part node in the hierarchy is stored in an individual JT file in a subdirectory with the same name as the assembly JT file.
  • Fully shattered - Each product structure node in the hierarchy is stored in an individual JT file. Monolithic - The entire product structure is stored in a single JT file.
  • PLMXML - An open XML-based file format, specified by Siemens Digital Industries Software. A PLMXML structure could link model data to another file (external representation), or the data can be integrated into the representation item in the XML file (internal representation).
  • STEP AP 242 XML - An ISO standard, which allows for representation of assembly data, metadata, kinematic data, etc. and linking model data to external references. In the global automotive industry, to achieve data exchange scenarios between companies, the use of STEP AP 242 XML and JT is recommended.

To help reduce 3D model storage and transmission bandwidth requirements, JT files can take advantage of compression. The use of compression is transparent to the JT data user, and a given model can be composed of JT files using different compression settings. The JT format has evolved through two forms of compression, standard compression uses a simple, lossless compression algorithm, while advanced compression uses a compression scheme supporting lossy geometric compression. Compression ratios are much greater with advanced compression. Standard compression support is maintained solely for backward compatibility with archived JT file visualization applications.

CAD Interop distributes several software to view, convert and compare JT files. Find below the list of our solutions compatible with the JT format: